2 Medicines and Healthcare products Regulatory AgencyMedical Devices Agency (MDA) and Medicines Control Agency (MCA) combined in April 2003New agency called the Medicines and Healthcare products Regulatory Agency (MHRA)MHRA is an executive agency of the Department of HealthOne of the MHRA services is to evaluate certain medical devicesAssessment of filters available on UK market

3 Use of breathing system filters5. A new, single-use bacterial/viral filter and angle piece/catheter mount must be used for each patient. It is important that these are checked for patency and flow, both visually and by ensuring gas flow through the whole assembly when connected to the circuit.CHECKING ANAESTHETIC EQUIPMENT 3 (Draft) Association of Anaesthetists of Great Britain and Ireland, 2003

15 Mass median diameter, MMDMass median aerodynamic diameterMass median diameter, MMDDiameter of particle such that 50% of the total mass of particles is contributed by particles with diameter > MMD, and 50% < MMDAerodynamic diameter, dada of a particular particle is the diameter of a spherical particle with a density of 1000 kg m-3 that has the same settling velocity as the particle